Vehicle engine coolant condition indicator



Jan. 31, 1967 W. J. SENSING VEHICLE ENGINE COOLANT CONDITION INDICATOR Filed 001;. 1, 1964 4o 7 m: 1i I 340 3; E: l I

INVENTOR. William J. Sens/n9 BY @QW His Attorney United States Patent 3,302,171 VEHICLE ENGINE COOLANT CONDITION INDICATOR William I. Sensing, Anderson, l[nd., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Oct. 1, 1964, Ser. No. 400,865 8 Claims. (Cl. 340-57) This invention relates to electrical indicating devices and more particularly to devices that give a visual indication of the condition of an engine cooling system.

It is common in vehicle engines to have an indicator visible to the operator of the vehicle which indicates the temperature of the cooling system. The purpose of this device is to alert the driver to an overheating condition so that it can be remedied before serious damage is done to the vehicle engine. It is common in the design of vehicle engines to have a pressurized cooling system which serves several purposes, one of which is to raise the boiling point of the coolant in the system. However, a situation can occur in an engine cooling system where the boiling point of the coolant in a pressurized system has not been reached but the system contains a boiling coolant because of a system leak. Therefore, it would be desirable to have an indicating system for an engine cooling system that is responsive to a temperature representing the boiling point of coolant in a pressurized system as well as being responsive to the boiling point of a coolant in a cooling system that is not pressurized.

It is an object of the present invention to provide an improved engine coolant condition indicator that is re sponsive to a plurality of temperatures.

It is another object of the present invention to provide an improved engine coolant condition indicator that is responsive to a plurality of temperatures as well as a pressure of the coolant.

It is still another object of the present invention to provide an improved engine coolant condition indicator that will provide a vehicle operator of an indication in the driving compartment when the engine coolant overheats in the pressurized or unpressurized condition.

It is a further object of the present invention to provide an improved engine coolant condition indicator that is very simple, economical to manufacture, and is compatible with engine cooling systems of common design.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred embodiment of the present invention is clearly shown.

In the drawing:

A diagrammatic view of the invention in its operative environment is illustrated.

Referring now to the drawing, an engine 10 is illustrated in operative association with a radiator 12 containing coolant that circulates between the engine 10 and the radiator 12 through lines 14 and 16. The lines 3rdand 16 cooperate with myriad passages, not shown, contained within the engine 10.

A thermal sensor 18 is disposed in the engine 10 at an appropriate place where the coolant temperature can be sensed and controls through a lead 20 the operation of a temperature responsive switch 22. The thermal sensor 18 preferably is a switch which can connect one side of relay coil 22a to ground. The thermal responsive switch 22 is designated on the drawing by T and in the preferred embodiment would be responsive through the sensor 18 to a temperature of approximately 240 F. The temperature responsive switch 22 is designed to selectively interrupt and close a circuit established between a battery 24 and an indicating light 26 through a lead 28 under the control of temperature responsive switch 22. It is noted that the inventive concept disclosed herein includes means responsive directly to temperature as well as indirectly as shown in the drawings.

A thermal sensor 30, disposed in temperature communication with another portion of the engine cooling system, is adapted to control through a lead 32 a temperature responsive switch 34 designated in the drawing by T The sensor 30 like sensor 18 preferably is a switch which can connect one side of relay coil 34a to ground. The switch T is adapted to selectively interrupt or make continuous an electrical path through a lead 36 which provides a path for current flow around the temperature responsive switch T A line 38 is connected on one end to the radiator 12 and on another end to a pressure responsive switch 40 which is designated in the drawing as P The switch P is in series with T and is adapted to selectively open or close a circuit established through the lead 36. It therefore becomes obvious that, when the switch T and the switch P are closed, a path for current flow is established around the switch T when the switch T is in the open position. It should be noted that the pressure switch P is held in the open position by a predetermined pressure and is allowed to close when the pressure in the radiator 12 falls below the predetermined pressure.

In operation, a coolant in the radiator 12 is communicated to the engine through passages 14 and 16 and is normally pressurized, while the engine is running, by a vapor pressure created by the heated coolant and by an engine driven coolant pump, not shown, which drives a cooling fan 42. The degree of pressurization of the system is determined in a given installation by engineering design factors. For the purposes of this illustration, it will be assumed that the system is pressurized to twelve pounds above atmospheric pressure. Under these operating conditions, the boiling point of the liquid can be near 240 F. Therefore, in the illustration given, the switch T will close at a temperature of 240 F. If pressurization in the engine cooling system is lost due to a leak in the system, the operating pressure of the system will be essentially atmospheric pressure. Under these pressure conditions, the boiling point of the coolant will be approximately 212 F. Therefore, in the example given, it will be assumed that the temperature responsive switch T closes at a temperature 212 F. The pressure responsive switch P is designed to hold itself in the open position until pressure in the radiator decreases to approximately two psi. above atmospheric. It is then clear that the temperature switch T and the pressure switch P are in series and generally responsive to the coolant condition when the cooling system is unpressurized and the temperature switch T is responsive to the coolant condition when the engine cooling system is pressurized.

If the pressurizing apparatus of the engine 10 is functioning normally and no leaks exist in the system, the switch T will close and complete a circuit from the battery 24 to the indicating lamp 26 through the lead 28 when the coolant temperature exceeds 240 F. Therefore, a vehicle operator will be apprised of an overheat condition of the coolant which would cause boiling of the coolant and damage to the cooling system. The vehicle can be very quickly halted and appropriate repairs made.

Under another set of operating conditions, the temperature responsive switch T responsive to 240 F. temperatures, would be ineffective to warn the vehicle operator of an overheat condition. As previously stated, when the pressure in the system is lowered, the boiling point of the coolant likewise lowers and the switch T responsive to 240 F. temperature, would not operate to close the circuit to the light 26. Without an alternate indicating system, an overheat condition of the engine cooling system might not be made known to the vehicle operator before serious damage to the system resulted.

However, the subject invention provides essentially a bypass around the switch T by providing a temperature switch T and a pressure switch P in series with the lead 36 around the temperature switch T Under operating conditions when pressure decreases in the cooling system due to a pump failure or a leak, the pressure would decrease in the line 38 to switch P causing the switch to close. However, an open in the lead 36 would still exist until the temperature switch T reached its operative temperature. This operative temperature, in the example given, is 212 F., representing the boiling point of Water at atmospheric pressure at sea level. Consequently, if pressure in the system is lost and an overheat condition does not result, the light 26 will not become incandescent. This would very commonly occur during a coolant level check of the radiator when the cap is removed. However, if the coolant temperature in the area of the thermal sensor goes to its boiling point during an unpressurized condition, the switch T will close. It is then clearly seen that, when the temperature switch T and the pressure switch P close, the lead 36 is made continuous and essentially short circuits the open temperature switch T to light the tell-tale lamp 26.

The utility of the present invention is obvious in the en vironment of a typical automobile cooling system. Using presently designed temperature indicating devices, an engine cooling system overheat condition can be had only under conditions when the system is pressurized. This is necessary in order to monitor the cooling system under normal operating conditions. When this is done, however, the possibility of an overheat condition occurring in the engine without the knowledge of the vehicle operator is possible if there is a pressure loss in the system. This invention is meant to obviate this problem.

It is emphasized that the temperature and pressure ranges illustrated in this specification are appropriate only for a system having water as a coolant and being pressurized to approximately twelve p.s.i. It is obvious that a coolant with a different boiling point could be used and pressurized to a different degree while still keeping within the spirit of the inventive concept recited herein. Temperature responsive switches of the type used in this invention and pressure responsive switches are available in a multitude of responsive ranges and might easily be incorporated into the system illustrated when a ditferent coolant is used or a diiferent pressure range desired. A typical example of a change in coolant in automobile engines might be in the use of a year-around coolant which is not pure water or in the use of a special coolant during the winter months. A change in the pressure switch might be initiated when one of the aforementioned coolants other than water is used or when the engine is to be operated under pressure conditions above or below sea level in a given installation for a long period of time.

While the embodiment of the present invention, as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

E, An indicating device comprising: an electrical power source; indicating means, means connecting one side of said indicating means to one side of said power source; first means responsive to a first temperature range to establish a conductive path between the opposite side of said electrical power source and the indicating means; second means responsive to a second temperature range; and third means responsive to a pressure range and cooperating with said second means to establish a conductive path between said opposite side of said power source and the indicating means.

2. An indicating device for a pressurizable engine cooling system, said device comprising: an electrical power source; indicating means connected to one side of said electrical power source; first means responsive to a first temperature range of the engine cooling system to complete a conductive path from the opposite side of said electrical power source to the indicating means, second means responsive to a second temperature of the engine cooling system; and third means responsive to a pressure range of the engine cooling system and cooperating with the second means to establish a conductive path between the opposite side of said electrical power source and the indicating means.

3. An indicating device according to claim 2 wherein the first means and second means are temperature switches.

4. An indicating device according to claim 3 wherein the first means is a temperature switch responsive to a temperature over 212 F.

5. An indicating device according to claim 3 wherein the first means is a temperature switch responsive to a coolant temperature of 240 F. when the coolant is at a pressure of more than two pounds.

6. An indicating device according to claim 3 wherein the second means is a temperature switch responsive to a temperature under 213 F.

7. An indicating device according to claim 2 wherein the third means is a pressure switch responsive to pressures of under two p.s.i.

8. An indicating device for a pressurizable engine cooling system that is operative to warn of a leak in the system or a restriction in coolant circulation, said device comprising: an electrical power source; indicating means encrgizable by said electrical power source; a first temperature responsive switch normally interrupting a path for current flow to the indicating means from the electrical power source and being responsive to a boiling point of the coolant in a pressurized cooling system to make continuous the path for current flow, a second temperature responsive switch normally interrupting a path for current flow to the indicating means from the electrical power source and being responsive to a boiling point of the coolant in an unpressurized cooling system, and a pressure switch in series with said second temperature responsive switch and responsive to a lowering of pressure in a pressurizable cooling system to make continuous an interrupted path for current flow from the electrical power source to said indicating means.

No references cited.

NEIL C. READ, Primary Examiner.

A. WARING, Assistant Examiner, 

1. AN INDICATING DEVICE COMPRISING: AN ELECTRICAL POWER SOURCE; INDICATING MEANS, MEANS CONNECTING ONE SIDE OF SAID INDICATING MEANS TO ONE SIDE OF SAID POWER SOURCE; FIRST MEANS RESPONSIVE TO A FIRST TEMPERATURE RANGE TO ESTABLISH A CONDUCTIVE PATH BETWEEN THE OPPOSITE SIDE OF SAID ELECTRICAL POWER SOURCE AND THE INDICATING MEANS; SECOND MEANS RESPONSIVE TO A SECOND TEMPERATURE RANGE; AND THIRD MEANS RESPONSIVE TO A PRESSURE RANGE AND COOP- 